1. Technical Field
The present invention relates generally to mobile communication systems and, more particularly, to a method and apparatus in a Universal Mobile Telecommunications System (UMTS) network for delivering short message service (SMS) messages.
2. Description of the Related Art
Wireless packet data networks are being deployed to provide connectionless wireless access to packet data networks. One wireless packet data network that is currently being deployed is General Packet Radio Service (GPRS). GPRS is a non-voice value added service that allows information to be sent and received across a mobile telephone network. It supplements, or rides on top of, today's circuit switched data and short message service networks. The theoretical maximum speed of GPRS includes speeds of up to approximately 171.2 kilobits per second (kbps). This maximum speed is achievable in GPRS systems using all eight timeslots at the same time in a Time Division Multiple Access (TDMA) context.
This speed is about three times as fast as data transmission speeds possible over today's fixed telecommunication networks and ten times as fast as current circuit switched data services on Global System for Mobile Communications (GSM) standard TDMA networks. Thus, GPRS systems are advantageous in that they require less system resources to transmit a fixed amount of data in comparison to using a traditional circuit switched approach. GPRS also facilitates instant connections in which information can be sent or received immediately as the need arises, subject to radio coverage. No dial up modem connection is necessary. GPRS, similar to some broadband connections for personal computers, often is referred to as being “always connected”. Thus, another one of the advantages of GPRS is that data may be transmitted immediately, whenever the need arises. In contrast to circuit switched data networks in which a connection must be established to transmit a data packet or data file, GPRS operation is extremely efficient in those situations in which a small amount of data is to be sent. As the emphasis of many designs today are to create wireless computer networks and to connect data devices, including personal computers to wireless transceivers and mobile terminals, such a system that provides instantaneous response is very important for time critical applications and, more generally, for the implementation of wireless computer networks. For example, a remote credit card authorization system implemented in a wireless network can be greatly improved if it is unnecessary for the customer to wait the amount of time that is required to establish a connection. Additionally, GPRS facilitates the use of Internet applications not only from personal computers, but also from appliances and machines. It is anticipated that appliances will be designed to be coupled to the Internet to facilitate control either onsite or remotely. While some people envision connecting these appliances to a network port by physical lines, it would clearly be advantageous to be able to connect such appliances to the Internet through a wireless link. GPRS will facilitate the creation of Internet controlled appliance networks through a wireless medium.
As suggested before, GPRS involves overlaying a packet based air interface on an existing circuit switched wireless network. For example, the circuit switched wireless network may comprise a GSM network. Accordingly, the user is given an option to utilize a packet based data service. In order to overlay a packet based air interface over a circuit switched network, the GPRS standard defines new infrastructure nodes to minimize the impact to existing networks in terms of hardware and software.
Another wireless packet delivery network being deployed, namely, a Universal Mobile Telecommunications System (UMTS) network, also provides connectionless services. A UMTS network includes a core network (CN), a UMTS terrestrial radio access network (UTRAN) and user equipment (UE). The core network provides switching, routing and transit for user traffic. Core network also contains the databases and network management functions. The basic Core Network architecture for UMTS is based on GSM network with GPRS. All equipment has to be modified for UMTS operation and services. The UTRAN provides the air interface access method for User Equipment.
One advantage of GPRS/UMTS is that the packet switching that results from the infrastructure nodes allows the use of radio resources only when users actually are sending or receiving data. Unlike traditional circuit switched voice networks, a connection is not continuously reserved for a user for the intermittent transmission of data. This efficient use of scarce radio resources means that larger number of GPRS users can share the same bandwidth and be served from a single base station or cell. The actual number of users that may use the system at one time, of course, depends on the amount of data being transferred.
The packet domain utilized in GPRS and UMTS systems uses a packet-mode technique to transfer high speed and low speed data and signaling in an efficient manner and generally optimizes network and radio resources. Strict separation between the radio subsystems and network subsystems is maintained, thereby allowing a network subsystem to be reused with other radio technologies. A common packet domain core network is used for both GSM and UMTS. The common core network provides packet switch services and supports differing quality of service levels to allow efficient transfer of non-continuous bit rate traffic (for example, bursty data transfers).
Under existing protocols and designs, a UMTS network establishes a signaling link as a part of establishing a data session. Once a user terminal has “attached” as a part of establishing its presence in the network (and control signaling is complete), the signaling link is torn down. More specifically, an Iu interface established between a radio network controller (RNC) and a serving GPRS support node (SGSN), and a radio resource controller (RRC) interface between the user terminal and the RNC, both for signaling, are released once the user terminal has attached and signaling for the attach procedure is complete. Accordingly, for any subsequent activities, the Iu and RRC interfaces must be re-established. Thus, if an SMS message is being stored in a short message service-service center (SMS-SC), the Iu and RRC interfaces must be re-established to deliver the stored SMS messages. Thus, if an SMS message is in queue and is to be delivered as soon as a user terminal is present, then the Iu and RRC interfaces are torn down and immediately re-established under present designs. Thus, present designs require additional signaling and interface setup and are not efficient when an activity is to take place immediately after a user terminal has attached.
There is a need, therefore, for a system and method that supports and provides more efficient processes relating to tear down of signaling links right after a mobile terminal has attached.